Hopper-type railroad cars are used to transport lading which is discharged through outlet gate assemblies mounted on discharge openings at the bottoms of the cars. Each outlet gate assembly includes a flat door or gate and a drive for moving the gate between open and closed positions. When closed, the gate prevents discharge of lading. When the gate is opened, the lading is free to discharge through the assembly. Latches are used to prevent opening of the gates by high energy impacts between rail cars.
Conventional gate assemblies use rack and pinion opening and closing drives to shift the gate between open and closed positions. Racks are mounted on the gate. A capstan on one end of an operating shaft is rotated in an appropriate direction to rotate pinion gears on the shaft, shift the racks and move the gate in a desired direction. The rack and pinion drives are mechanically connected to a movable latch by a lost motion latch drive. The latch is positively retracted during initial rotation of a capstan, prior to initial movement of the closed gate in the opening direction. The latch must be withdrawn before the gate moves. During impact the latch can become wedged or hooked in place while holding the gate closed.
Another conventional gate assembly uses a rack and pinion drive including a resilient member positioned between adjacent teeth on a rack. The resilient member engages a tooth of a pinion gear to prevent accidental opening. Rotation of the pinion gear deforms the resilient member to allow the gate to be moved from the closed locked position to the open, unlocked position.
Each of the above conventional gate assemblies is latched by a mechanism forming part of the gate opening and closing drive. These latch mechanisms cannot be used with other types of gate opening and closing drives because the latching mechanism is an integral part of the particular drive. Many of the gate assemblies require a lost motion latch drive to open the latch prior to moving the gate in the opening direction. Such latch drives are difficult and costly to manufacture and install.
Further, wedge-type latches can become jammed against the gate by impact, making unlatching and opening of the gate difficult.
Thus, there is a need for an improved outlet gate assembly having a latch mechanism that automatically latches and unlatches the gate, independently of the gate opening and closing drive. The latch must hold the gate closed on impact, yet permit jam-free opening of the gate by the opening and closing drive.